The present invention relates to multi-functional electrode devices for fast-charging of energy-storage devices and methods therein.
Modern electronic appliances are becoming ubiquitous for personal, as well as business use. It cannot be overstated that with the evolution of such devices, mobility has emerged as a key driver in feature enhancement for technological innovation. While the rapid advancement of low power-consumption processors and flash-memory devices have enabled such mobility to reach new levels of real-world productivity, further development is significantly hampered by the rather slow progress made in battery technology. The proliferation of smart phones, tablets, laptops, ultrabooks and the like (acquiring smaller and smaller form factors) has made this issue even more abundantly apparent as consumers are eager to have longer and longer device usage periods between recharge cycles, without adding heft to the weight and footprint of such devices.
Furthermore, electrical and electronic components that don't fall under the mobile rubric are also in need of extended usage solutions. Such components include devices having sporadic power-source connection (e.g., backup emergency sentinels, remotely-stationed telecommunication repeaters, electric vehicle console communicators, as well as off-shore communication, control, and positioning devices).
The demands of such applications vary widely, for example, in voltage or power level, butallare preferably served by lightweight, power-storage devices which can rapidly and consistently provide high energy density over long time spans, and can be quickly recharged to operational energy levels. To date, such extensive mobile energy needs are being met in part by one of two available types of power-storage devices: rechargeable batteries (e.g., lithium-ion intercalation systems) or supercapacitors (e.g., Faradic pseudo-capacitive type, non-Faradic double-layer reaction types, or hybrid types).
To meet the growing demand in portable electronic devices and devices having sporadic power-source connection, energy storage devices with high specific energy, high power density, long cycle life, low cost, and a high margin of safety must be employed.
Currently, the dominant energy storage device remains the battery, particularly the lithium-ion battery (LIB). LIBs power nearly every portable electronic device, as well as almost every electric car, including the Tesla Model S and the Chevy Volt. Batteries store energy electrochemically, in which chemical reactions release electrical carriers that can be extracted into an electrical circuit. During discharge, the energy-containing lithium ions (Li ions) travel from a high-energy anode material through an electrolyte and a separator to a low-energy cathode material. The electrochemical reaction, taking place in the discharging process, involves internal movement of Li ions from the anode to the cathode, and the release of electrons (e.g., energy) at the anode, which are extracted to the external circuit in order to operate whatever device needed.
During battery charging, energy is used to transfer the Li ions back to the high-energy anode assembly. The charge and discharge processes in batteries are slow processes, and can degrade the chemical compounds inside the battery over time. A key bottleneck in achieving enhanced performance is the limited fast-charging ability of any standard battery. Rapid charging causes accelerated degradation of the battery constituents, as well as a potential fire hazard due to a localized, over-potential build-up and increased heat generation—which can ignite the internal components, and lead to explosion.
For example, LIBs have the highest energy density of rechargeable batteries available, but typically suffer from low power by virtue of reversible Coulombic reactions occurring at both electrodes, involving charge transfer and ion diffusion in bulk electrode materials. Since both diffusion and charge transfer are slow processes, power delivery as well as the recharge time of Li ion batteries is kinetically limited. As a result, batteries have a low power density, and lose their ability to retain energy throughout their lifetime due to material degradation.
On the other extreme, electrochemical double-layer capacitors (EDLCs) or ultracapacitors are, together with pseudocapacitors, part of a new type of electrochemical capacitors called supercapacitors (hereinafter referred to as SCs), which store energy through accumulation of ions on an electrode surface, have limited energy storage capacity, but very high power density. In such SCs, energy is stored electrostatically on the surface of the material, and does not involve a chemical reaction. As a result, SCs can be charged quickly, leading to a very high power density, and do not lose their storage capabilities over time. SCs can last for millions of charge/discharge cycles without losing energy storage capability. The main shortcoming of SCs is their low energy density, meaning that the amount of energy SCs can store per unit weight is very small, particularly when compared to batteries.
The most intuitive approach to combine high energy and high power density within a single device is to combine different types of energy storage sources. So far, such hybrid power-source devices involving SCs and batteries have mainly been explored in view of parallel connection (i.e., an SC is being used as a power supply, while the battery is used as an energy source, which supplies energy both to the load and to the SC, which in turn, should be charged at all times). The contribution of components to the total stored charge is not optimal, due to the minimal use of the SC, and the higher degradation of the battery due to the additional charging of the SC.
In the prior art, Vlad et al. published an article entitled, “Hybrid supercapacitor-battery materials for fast electrochemical charge storage,” (Scientific Reports, 4, Article No. 4315, 2014) which presents an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a LIB material (LiFePO4). The same authors published online supplementary material to the Scientific Reports article (www.nature.com/srep/2014/140307/srep04315/extref/srep04315-s1.pdf). Furthermore, an international application was filed with some of said authors as the inventors for “Hybrid electrode for non-aqueous electrolyte secondary battery” (PCT Patent Publication No. WO 2015/032950 A1).
It would be desirable to have multi-functional electrode devices for fast-charging of energy-storage devices and methods therein. Such devices and methods would, inter alia, overcome the various limitations mentioned above.